Left hamstring problem

I use to skate nearly every day for the last six months or so, but I have stopped, and since I am have started back to skate, since I'm only 17 long boarding is a hobby.

I have noticed on legs day when I do leg curls for hamstrings that I have some pain in the left sting of my hamstring on my left leg.

Even with medium weights like 40-50 on the machine I can feel my hamstring almost like a grinding action and feels like it's going to tear.

I was wondering weather or not any experienced forum members would know if/what the problem is, weather it would be micro years through it or what, I'm a little concerned about it and would love to hear your feedback on the matter.

This sounds crazy but do you stretch or warm up? Also, does it hurt to the touch? or does pain arise during certain movements (not excercises) example, rotation, flexing, bending, squatting, etc..
Any visible bruises? or swelling?

This sounds crazy but do you stretch or warm up? Also, does it hurt to the touch? or does pain arise during certain movements (not excercises) example, rotation, flexing, bending, squatting, etc..
Any visible bruises? or swelling?

Yeah I stretch and warm up, no not at all, it just feel like it's grinding on something when I feel it mid contraction on leg curls. It's only little pain when I contract, it feels like it going to tear